1. Field of the invention
This invention relates to a crankcase emission control system or a crankcase ventilation system for an internal combustion engine, such as a V-type internal combustion engine.
2. Description of the Prior Art
In internal combustion engines, compressed air-fuel mixture and combustion products leak from combustion chambers into a crankcase past piston rings. This leakage is called "blow-by gas". Since blow-by gases contain harmful components, it is necessary to prevent them from venting to the atmosphere.
A crankcase emission control system or a crankcase ventilation system returns blow-by gases back to combustion chambers in order to prevent their emission into the atmosphere.
U.S. Pat. No. 3,661,128 discloses a crankcase ventilation system for a V-type internal combustion engine. This system includes passages which return blow-by gas from a crankcase to combustion chambers. Since peak pressures within the combustion chambers increase with the engine load, the rate of the gas leakage into the crankcase also increases with the engine load. In this system, the sum of the effective cross-sectional areas of the blow-by gas return passages is generally limited to a relatively small value, so that the speeds of the blow-by gas flows in the return passages are relatively high at heavy engine loads. The crankcase also defines a reservoir of engine lubricating oil. As the speeds of the blow-by gas flows in the return passages increase, the rate of lubricating oil undesirably entrained or carried by these gas flows from the crankcase to the combustion chambers increases. Accordingly, in this system, the engine lubricating oil is dissipated or wasted at a relatively high rate when the engine load is heavy.